Editor's Note: This story was updated at 4:50 p.m. ET to
reflect additional statements from NASA. Contrary to the previous report, NASA
denies it is undertaking any effort to look specifically for sabotage.

NASA does not suspect sabotage was behind the glitch that
twice delayed the launch of the space shuttle Endeavour recently.

The agency is investigating all possible explanations for
the problem, but has no specific processes to search for intentional tampering,
officials said.

"NASA is not concerned about sabotage at all,"
NASA spokesman Kyle Herring said. "They develop a detailed fault tree to
try to come to a conclusion as to what the problem is. The program leaves no
stone unturned in an investigative effort. There is never a fault tree that has
a block in it that?s labeled sabotage."

Endeavour's STS-127
mission was supposed to lift off June 13, but a leak of hydrogen gas from a
pipe attached to the shuttle's fuel tank kept the vehicle grounded. NASA tried
to launch Endeavour a second time on Wednesday, but again the leak appeared,
even after workers replaced the leaky seal between the pipe and the shuttle.

The shuttle will now stand down until at least July 11 while
investigators probe the cause of the failure, which also delayed the shuttle
Discovery's STS-119 mission in March. That flight managed
to blast off four days later than planned, after the seal swap-out
apparently stopped the leak.

So far, the root cause of the issue is mysterious.

"We've got to step back and try to understand this
problem," space shuttle deputy program manager LeRoy Cain said in a
briefing after the second Endeavour delay. "I'm confident we will do that.
We will be relentless in terms of trying to understand what's going on with
this system."

While NASA fully expects to find a technical glitch at
fault, its investigative processes will be able to detect any human-introduced
error as well, if it occurred, Cain said.

NASA plans to retire its three aging space shuttles in 2010,
though its next-generation
spaceship, called Orion, will not be ready by then.

The agency began cutting
shuttle-related jobs last month and expects to have to lay off a
significant number of workers after the last shuttle flies. Because each
shuttle launch delay has ripple effects on future scheduled flights, the stall
with Endeavour has the potential to extend the shuttle fleet's end date. NASA
is mindful that some workers may be under stress due to the situation.

"We have talked a great deal about those kinds of
potential issues," Cain said. "And I think we're taking measures that
are commensurate with the circumstances that we have here as we go forward this
summer and for the rest of the shuttle program for sure."

He said he doubted anyone on staff would try to sabotage the
program.

"I think that we've got a highly professional work
force here, and to a person, at least when I talked to them, they're in this
business because they love the work that they do and they love to support the
human spaceflight endeavor."

A case of sabotage has
occurred before, with a subcontractor working on the 2007 flight of
Endeavour. NASA discovered a space station computer box that was intentionally
damaged, with cut wires. They were able to repair the damage with no ill
effects to the flight.

In this situation, though, NASA has stressed that there is
no reason to suspect intentional tampering, and they are not taking any
particular steps to investigate this possibility.

"We trust the people who work on this program and we'll
do anything we can to help them understand and correct a problem," Herring
said. "We know it?s a dedicated work force. Any problems of any kind we
would uncover through our normal checks and balances."

In response to any suggestion of sabotage, United Space
Alliance, a major NASA contractor on the shuttle, released a statement.

"Any suggestion that our workforce would do anything to
intentionally hinder a safe and successful launch is grossly irresponsible and
completely off-base. The entire shuttle team worked extremely hard making the
necessary repairs and preparing Endeavour for the July 17th launch
attempt.? It is a testament to their dedication, commitment and skill that the
vehicle was in a position to go for the second attempt. Neither USA nor our
NASA customer has any reason to suspect any wrongdoing of any kind, and there
is no investigation being undertaken."